Enhancing environmental performance during Wheatstone dredging through science and innovation

Dredging for the Chevron-operated Wheatstone LNG Project, near Onslow, Western Australia, involved movement of approximately 30 Mm3 of material over 23 months to provide safe navigation for LNG export as well as trunkline installation and stabilisation. Dredging was carried out in a sub-tropical, inshore environment near to biological benthic communities including corals, seagrasses, macroalgae and filter feeders, deemed sensitive to elevations in turbidity and/or sedimentation associated with dredging. Science and innovative technology was used to proactively and adaptively management dredging in order to afford a high level of environmental protection. Water quality data was transmitted via satellite to Perth where it was compared, daily, against management triggers derived from scientific analysis of an extensive dataset collected during a previous, nearby, dredging program. Accurate hindcast modelling, combined with MODIS satellite imagery, provided oversight of the extent and cause of observed turbid plumes, while forecast modelling provided predictions of the potential impacts of upcoming dredging activities, allowing for proactive changes to dredging activities to minimise potential impacts. Monitoring of benthic communities was undertaken using remotely operated underwater vehicles (ROVs) and water quality monitoring in the latter part of the program was undertaken using remotely operated Wave Gliders (Liquid Robotics), both of which resulted in significant safety improvements and cost savings and over traditional monitoring methods. Post-dredging surveys of benthic communities indicated that, despite their proximity to dredging activities and the enormity of dredged volumes, no detectable impacts had occurred as a result of dredging.